Through the first six weeks of the year, flight tracker masFlight estimates that there were 75,000 canceled flights at U.S. airlines, the largest number since U.S. airspace was shutdown following the Sept. 11 terrorist attack.

JetBlue Airways(JBLU), which operates 45% of its flights through New York or Boston, has also been hit hard. It warned in early January that 1,800 canceled flights the first week of the year would cost it $45 million in revenue and $30 million in profits.